Synthesis method of stable paranitroaniline diazonium salt

Abstract

The invention discloses a stable paranitroaniline diazonium salt synthesis method, which comprises: washing a sulfonic acid resin with deionized water, adding into a reaction kettle, preparing a certain amount of deionized water, adding into the reaction kettle, starting stirring, and uniformly mixing; then slowly adding paranitroaniline into the reaction kettle for multiple times for dissolving, uniformly stirring until no obvious solid residues exist on the liquid surface, setting the temperature, injecting a fresh sodium nitrite solution into the reaction kettle, and after the reaction is finished, filtering, washing and drying the mixture. And adding the obtained diazonium salt into deionized water and carrying out substitution reaction with quantitative potassium iodide to obtain 4-nitroiodobenzene to indirectly calculate the yield. The diazonium salt is subjected to an ARC thermal stability test to prove that the diazonium salt is relatively good in thermal stability and can be stored for a relatively long time at room temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical industry, and in particular to a method for synthesizing a stable p-nitroaniline diazonium salt. Background Art

[0002] Diazo compounds are highly reactive and can undergo coupling reactions with aromatic compounds with hydroxyl or amino groups, and can also undergo free radical reactions with benzene, nitrobenzene or certain metal salts. Compared with other organic compounds, it is quite unstable and easily decomposed by light and heat. It is easy to explode when heated or vibrated in a dry state. If the temperature and pH value remain unchanged when left standing, it will decompose according to the kinetic first-order reaction. Due to the strong activity of diazo compounds, there are problems with storage stability in the printing and dyeing industry and in the application of photographic films. Among azo dyes, dyes with weakly alkaline aromatic amines as diazo components have excellent light fastness due to the introduction of strong electron-withdrawing groups in aromatic amines, and are an important component of disperse dyes.

[0003] Common weakly alkaline aromatic amines include 2,4-dinitroaniline, 4-nitroaniline, 2,6-dichloro-4-nitroaniline, 2,4-dinitro-6-chloroaniline, etc. Although the theoretical amount of strong acid such as concentrated sulfuric acid is only 2 times the molar amount in the diazotization process of such aromatic amines, these weakly alkaline aromatic amines are generally weak in alkalinity and are difficult to completely dissolve even in concentrated acid; at the same time, the diazonium salts formed after the diazotization of these aromatic amines are generally less stable and need to be stably present under conditions such as concentrated acid and low temperature. Therefore, the diazotization reaction of such aromatic amines often needs to be carried out in 10 times or more of concentrated sulfuric acid. This has resulted in the generation of a large amount of acid wastewater, which has become a bottleneck restricting the clean production of large-tonnage disperse dyes in my country.

[0004] On the other hand, weakly basic aromatic amine has larger solubility in some organic solvents, and diazotization reaction is carried out in solvent, and the use of a large amount of concentrated acid can be avoided. However, in the presence of no a large amount of concentrated acid in solvent, how to obtain stable diazonium salt and carry out next step coupling reaction is also a larger problem. Some people also adopt fluoroboric acid etc. as diazonium salt stabilizer at home and abroad, and prepare the diazonium salt filter cake of weakly basic aromatic amine in acid or solvent, and this filter cake can still stably exist under the condition that no a large amount of inorganic strong acid exists. But it is more costly to prepare fluoroboric acid diazonium salt, and it carries out subsequent coupling or self-decomposition and all can produce F2, causing larger pollution. Summary of the invention

[0005] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a method for synthesizing a stable p-nitroaniline diazonium salt. The method can use only water as a solvent, and the diazonium salt can be directly separated after the reaction is completed. In addition, the synthesized diazonium salt has good thermal stability, is not easily decomposed under normal process conditions, and is safe, green and environmentally friendly.

[0006] The technical solution of the present invention is: a method for synthesizing a stable p-nitroaniline diazonium salt, comprising the following steps:

[0007] (1) First, the sulfonic acid resin is washed with deionized water to remove residual inorganic acid and some impurities;

[0008] (2) adding the impurity-removed sulfonic acid resin, p-nitroaniline and deionized water into a reaction kettle and stirring evenly until there is substantially no solid residue on the liquid surface;

[0009] (3) injecting fresh sodium nitrite solution into the reactor, keeping the temperature at a certain temperature for a period of time, and after the reaction is completed, filtering the mixture, washing and drying to obtain the target diazonium salt.

[0010] Preferably, the molar ratio of p-nitroaniline, sodium nitrite and sulfonic acid resin is 1:1-2:1.8-3.5.

[0011] Preferably, the reaction temperature is controlled at 15-35°C and the reaction time is 30-60 min.

[0012] Preferably, the mass fraction of the sodium nitrite solution is 25-35%, and the injection speed of the sodium nitrite solution is 0.2-0.5 mL / min.

[0013] Compared with the traditional diazonium salt synthesis method, the present invention has the following significant advantages: (1) water is used as the solvent, no waste acid is generated, and it is green and environmentally friendly; (2) the synthesized diazonium salt has good stability and can be stored for a long time at room temperature; (3) the resin used can be recycled after the subsequent reaction is completed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Comparison of infrared spectra of synthesized diazonium salt and sulfonic acid resin.

[0015] Figure 2 This is the p-INB HPLC test result.

[0016] Figure 3 is the time when the maximum decomposition reaction rate reaches TMR under adiabatic conditions ad Relationship with temperature. DETAILED DESCRIPTION

[0017] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the implementation methods and the accompanying drawings.

[0018] The synthesis equation of diazonium salt of the present invention is:

[0019]

[0020] The instruments used are:

[0021] Glass rod, beaker, Buchner funnel, low-temperature constant temperature bath, syringe pump, measuring cylinder, rubber-tipped dropper, constant speed stirrer, iron stand, drug injection tube, round-bottom flask.

[0022] Embodiment 1:

[0023] The molar ratio of p-nitroaniline (p-NA) and sulfonic acid resin (A-15) was 1:2.3. The temperature was controlled at 30°C, stirring was started, and freshly prepared sodium nitrite solution was added within 5 minutes. The reaction time was 60 minutes. After the reaction was completed, the mixture was filtered and washed to obtain a diazonium salt mixture. After measurement, it was determined that the conversion rate of the raw material p-nitroaniline exceeded 99%. The diazonium salt was converted into 4-nitroiodobenzene with a sufficient amount of potassium iodide, and the yield reached 80%, that is, the yield of the diazonium salt reached 80%. The purity of 4-nitroiodobenzene was tested by high performance liquid chromatography and exceeded 96%. Figure 1 .

[0024] The diazonium salt mixture was characterized by infrared spectroscopy. Figure 2 . IR(KBr), -N≡N-: 2297.66, -NO2: 1540.45(v as ) and 1349.85(v s )cm -1 . .

[0025] Embodiment 2:

[0026] The other steps and process parameters are the same as those in Example 1, except that the molar ratio of sodium nitrite is changed. The results of component analysis are shown in Table 1 below.

[0027] Table 1 Effect of sodium nitrite content on the results during diazotization

[0028]

[0029] From the above results, it can be seen that the optimal molar ratio of sodium nitrite to p-nitroaniline in this process is 1.2.

[0030] Embodiment 3:

[0031] The other steps and process parameters are the same as those in Example 1, except that the reaction temperature is changed. The results of component analysis are shown in Table 2 below.

[0032] Table 2 Effect of temperature on the results during diazotization

[0033]

[0034] From the above results, it can be seen that the optimal temperature in this process is 25-30°C.

[0035] Embodiment 4:

[0036] The other steps and process parameters are the same as those in Example 1, except that the amount of resin added is changed. The results of component analysis are shown in Table 3 below.

[0037] Table 3 Effect of resin content on the results during diazotization

[0038]

[0039] From the above results, it can be seen that the equivalent ratio of resin to p-nitroaniline in this process can be greater than 2 and cannot be less than 2.

[0040] The diazonium salt mixture prepared in Example 1 was subjected to thermal stability analysis, and the test process and results (Table 4) are as follows:

[0041] Test conditions:

[0042] Test mode: heating-waiting-searching

[0043] Detection sensitivity: 0.02℃ / min

[0044] Temperature range: 25-150℃

[0045] Heating step: 5℃

[0046] Waiting time: 15 minutes

[0047] Test sample ball: titanium ball (Ti), mass 5.95g

[0048] Sample mass: 1.77g

[0049] Table 4 ARC thermal stability test processing parameters and results

[0050] parameter Numeric Sample weight / g 1.77 The mass of the ball / g 5.95 <![CDATA[Sample specific heat C p.s (J·g -1 ·K -1 )]]> 1.443 <![CDATA[Specific heat capacity C of the ball p.b (J·g -1 ·K -1 )]]> 0.523 Thermal correction factor (Ф) 2.22 Initial decomposition temperature (℃) 55.55 Maximum heat release rate (℃ / min) 3.0 Temperature corresponding to the maximum heat release rate (℃) 103.43 Decomposition end temperature (℃) 111.65 <![CDATA[Corrected adiabatic temperature rise ΔT ad (K)]]> 124.54 <![CDATA[Specific heat release (J·g -1 )(after Ф value correction)]]> 179.7

[0051] This shows that the diazonium salt has good stability and T D24 About 43.6℃ (see Figure 3 ), it can be stored for more than 10 days at 30°C and nearly 20 days at 25°C. Figure 3 Medium TMR ad is the time when the maximum decomposition reaction rate is reached under adiabatic conditions.

Claims

1. A method for synthesizing a stable p-nitroaniline diazonium salt, characterized in that: The steps include: (1) First, wash the sulfonic acid resin with deionized water to remove residual inorganic acid and some impurities; (2) adding the impurity-removed sulfonic acid resin, p-nitroaniline and deionized water into a reaction kettle and stirring evenly until there is substantially no solid residue on the liquid surface; (3) Inject fresh sodium nitrite solution into the reactor and keep it at a certain temperature for a period of time. After the reaction is completed, filter the mixture, wash and dry it to obtain the target diazonium salt.

2. The method according to claim 1, characterized in that The molar ratio of p-nitroaniline, sodium nitrite and sulfonic acid resin is 1:1~2:1.8~3.

5.

3. The method according to claim 1, characterized in that Control the reaction temperature to 15~35℃ and the reaction time to 30~60min.

4. The method according to claim 1, characterized in that The mass fraction of sodium nitrite solution is 25~35%.

5. The method according to claim 1, characterized in that The injection rate of sodium nitrite solution is 0.2~0.5mL / min.

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